In praise of germs: Why common bugs are necessary for kids

Attention, germaphobes. Exposure to the microscopic bugs is crucial for keeping kids healthy, according to new research in the prestigious journal Science. The study strongly supports a growing body of evidence that you need to put away the disinfectant and expose children to the real world of germs and microbes.

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We're meant to encounter some microbes and dirt when we're young. It's how we build our immune systems.

Scientists Richard S. Blumberg and Dennis L. Kasper and a team of researchers at Harvard Medical School showed that in mice exposure to germs in early life helped reduce the body’s inventory of invariant natural killer T (iNKT) cells. These cells help protect us against diseases like inflammatory bowel disease and asthma. But, if there are too many of them with too much time on their hands, they can actually cause these conditions. By exposing young mice to common microbes the scientists saw that the animals were protected from accumulating T cells -- and were healthier than those who were not.

The scientists reached an admittedly geeky conclusion: “These results indicate that age-sensitive contact with commensal microbes is critical for establishing mucosal iNKT cell tolerance to later environmental exposures,” they wrote in the journal Science. In other words, exposing baby mice to common germs got their immune systems appropriately busy and able to not over-react when encountering nasty bugs and other biological stuff later in life.

This is a big deal.

The rapid rise in food allergies, asthma and other immunological diseases is due, at least in part, to our modern obsession with cleanliness, scientists increasingly believe. The 'hygiene hypothesis', first advanced in 1989 by the British epidemiologist David Strachan, contends that these diseases are becoming more common because young children are not exposed to them at an early age. We spend so effort trying to prevent exposure to germs with antibiotics, antibacterials and soaps that letting kids get dirty seems like a violation of basic parental duty.

Parents are constantly being told to make their kitchens spotless, to kill 99.9 per cent of the germs lurking in their bathrooms and to wash themselves and their babies all the time.

This world of purity sounds good but it does not fit how we are designed. We are meant to encounter some microbes and dirt when we are young. It is how we built our immune systems. We need a certain amount of grunginess as kids to be healthy adults.

As the Harvard study shows, filth can be good -- at least in tiny amounts when you are very young.

Arthur Caplan, Ph.D., is a Professor in the Department of Medical Ethics and Health Policy at the University of Pennsylvania